Environmental impacts from acid sulfate soils (ASS) result from the characteristics of the pore water chemistry, yet there has been only limited research in this area due to the difficulties in sampling the pore waters of these soils. This book reports the use of in-situ, diffusion-controlled, dialysis samplers to follow spatial changes in pore water chemistry of ASS profiles in an estuarine floodplain of eastern Australia. The environment of deposition of the Holocene-age ASS was determined by fossil analysis of pollen, forams, and shells. The upward stratigraphic transitions from terrestrial freshwater, to marine, to estuarine, to terrestrial freshwater were determined, and estimates made of the aquatic salinities and ecologies. Mineral phases predicted from the pore water chemistry were confirmed by XRD analysis. A diffusion analysis of the pore water profiles estimated the time of sulfide oxidation and minimal rate of acid production at the site. The chloride concentration profile gave an upward flux of about 660 kg/ha.yr and a time of about 2000 years for the profile's exposure to fresh surface waters.